1. Field of the Invention
The present invention relates to operation control for a camera comprising a program control means consisting of a microcomputer.
2. Related Background Art
Recent cameras comprise microcomputer to perform an automatic light-metering or exposure process under the program control, as well as an auto-focus process by interlocking an auto-focus device with a motor for moving an imaging lens. Thus, automatic focusing is performed to always provide optimal imaging conditions.
The following process of an automatic camera are sequentially performed under the program control of a microcomputer upon depression of a shutter release button: a battery check process for checking a dry-cell voltage; a light-metering process for checking an apertures; a low-luminance process for determining, from luminance of an object, if auxiliary illumination (e.g., a flash device) is necessary, and if necessary, for signaling for the use of the flash device; and a discrimination process for checking if the flash device is used. Next, a focusing process is performed by an auto-focus device. After the focusing process is completed, an exposure control process is performed under the control of the microcomputer. In this way, program control of a microcomputer plays an increasingly important role in modern camera function.
However, the following problems are presented.
When the auto-focus device is operated, a motor is driven to move an imaging lens. If this operation is performed during the operation of the microcomputer, the microcomputer is adversely influenced by noise produced by the motor or variations in power source voltage due to current load, and is erroneously operated, thus interrupting normal operation control of the camera.
In order to overcome this, a control mechanism which produces noise and the microcomputer can be time-divisionally operated. For example, during the auto-focus operation, power supply to the microcomputer is cut off or an operation interruption signal is applied thereto to interrupt its operation. During this interruption, the motor or the like is operated, and after the auto-focus operation is completed, the microcomputer is again energized.
However, when the microcomputer is restarted after cutting off the power supply or resetting thereof, the program control starts again from an initial program step. As a result, only the portion of the computer program processed before the microcomputer power supply was interrupted is executed, and an imaging process based on the remaining portion of the program cannot be executed.
For example, when the microcomputer is enabled upon depression of a shutter release button, a pre-focusing process (e.g., battery check, luminance determination, and the like) is executed, and a focusing operation is then performed by the auto-focus device while disabling the microcomputer. After the focusing operation is completed, the microcomputer is again enabled. In this case, program control to be performed after the focusing operation (to be referred to as an after-focusing process hereinafter) cannot be executed. In other words, if the focusing operation is to be executed between the pre-focusing and after-focusing processes under the program control of the microcomputer, the latter cannot be performed.
Note that the pre-focusing process can be combined with the control steps of the after-focusing process, and after the auto-focus operation is completed, only the program control of the microcomputer need be performed, thus eliminating the adverse influence on the microcomputer. However, if focusing must be adjusted upon the use of the flash device the microcomputer must determine before the auto-focus operation if the flash device is to be used and set various data therefor. In order to control the operation of such a complicated camera, the processes of the microcomputer are inherently mixed with the those of other mechanisms.